ERR_HS_SYNC_LATENCY on HubSpot: HubSpot Property History Shows Delayed or Missing Sync Data. Root cause: HubSpot property history sync is delayed, showing stale data or not updating in real-time. Common causes: property history tracking not enabled, sync frequency set to low interval (daily/weekly), API rate limits throttling, property history retention expired, integration batching updates instead of real-time, webhook subscriptions not configured. Step 1: Implement Polling with Backoff. After writing a property update, do not immediately poll for the change. Wait at least 60 seconds before the first read, then use exponential backoff (60s, 120s, 240s) for subsequent checks. Most updates propagate within 5 minutes. Step 2: Use Webhooks Instead of Polling. Subscribe to HubSpot property change webhooks via the Webhooks API. Webhooks fire after the change has propagated, eliminating the race condition between write and read. This is the recommended approach for real-time integrations. Step 3: Check for Sync Conflicts. If multiple systems are writing to the same HubSpot property simultaneously, the last write wins but the history may show out-of-order entries. Implement a source-of-truth field (e.g. last_modified_by) to detect and resolve conflicts.